1. Field of the Invention
The present invention relates to a plain bearing comprising an aluminum (Al) alloy, and a method of manufacturing the same.
2. Description of the Related Art
A plain bearing comprising an Al alloy has been usually manufactured through the following steps. That is, the steps include casting the Al alloy, then annealing it, facing it, cladding it with pure Al plate, rolling the clad Al plate, and finally cladding the rolled plate with a steel plate constituting a back metal. In this case, the Al alloy contains comparatively soft tin (Sn) or comparatively hard silicon (Si) in order to improve a bearing properties.
However, the above manufacturing method has the following problems. First, the Al alloy contains Si as hard particles. In order to roll the Al alloy plate as described above, an amount of Si contained in the Al alloy has to be 4 mass % at maximum. This is because ductility of the Al alloy is reduced, and the Al alloy may break in rolling, if the Al alloy contains a large amount of Si. Therefore, the amount of Si cannot be increased.
Moreover, because the Al alloy contains a large amount of Sn, the Al alloy cannot be directly clad to a steel. It is because a sufficient bonding to steel cannot be obtained due to Sn. Therefore, in order to bond the Al alloy to the steel, it is necessary to dispose an intermediate layer of pure Al, because the pure Al does not contain Sn and has ductility. However cost increases unavoidably by adding this step.
It is to be noted that JP-A-59-221479 discloses a swash plate rotated on an axis in a swash plate type compressor for use in an air conditioning system of a vehicle. The swash plate is manufactured as follows. Si powder is linearly applied to the sliding surface of a base material formed of an Al alloy (A390), and then laser beam is irradiated on the Si powder. The Si powder and the base material around the powder are molten, and thereafter solidified to form a hardened layer having a high Si content, on the surface of the base material.
In the plain bearing comprising the Al alloy, there has been a demand for further improvement of resistance to wear and seizure in recent years, but a plain bearing having the above conventional constitution can not satisfy the demand.